5,793 research outputs found

    Detection of selfish manipulation of carrier sensing in 802.11 networks

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    Recently, tuning the clear channel assessment (CCA) threshold in conjunction with power control has been considered for improving the performance of WLANs. However, we show that, CCA tuning can be exploited by selfish nodes to obtain an unfair share of the available bandwidth. Specifically, a selfish entity can manipulate the CCA threshold to ignore ongoing transmissions; this increases the probability of accessing the medium and provides the entity a higher, unfair share of the bandwidth. We experiment on our 802.11 testbed to characterize the effects of CCA tuning on both isolated links and in 802.11 WLAN configurations. We focus on AP-client(s) configurations, proposing a novel approach to detect this misbehavior. A misbehaving client is unlikely to recognize low power receptions as legitimate packets; by intelligently sending low power probe messages, an AP can efficiently detect a misbehaving node. Our key contributions are: 1) We are the first to quantify the impact of selfish CCA tuning via extensive experimentation on various 802.11 configurations. 2) We propose a lightweight scheme for detecting selfish nodes that inappropriately increase their CCAs. 3) We extensively evaluate our system on our testbed; its accuracy is 95 percent while the false positive rate is less than 5 percent. Š 2012 IEEE

    Effects of communication efficiency and exit capacity on fundamental diagrams for pedestrian motion in an obscure tunnel|a particle system approach

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    Fundamental diagrams describing the relation between pedestrians speed and density are key points in understanding pedestrian dynamics. Experimental data evidence the onset of complex behaviors in which the velocity decreases with the density and different logistic regimes are identified. This paper addresses the issue of pedestrians transport and of fundamental diagrams for a scenario involving the motion of pedestrians escaping from an obscure tunnel. % via a simple one--dimensional particle system model. We capture the effects of the communication efficiency and the exit capacity by means of two thresholds controlling the rate at which particles (walkers, pedestrians) move on the lattice. Using a particle system model, we show that in absence of limitation in communication among pedestrians we reproduce with good accuracy the standard fundamental diagrams, whose basic behaviors can be interpreted in terms of the exit capacity limitation. When the effect of a limited communication ability is considered, then interesting non--intuitive phenomena occur. Particularly, we shed light on the loss of monotonicity of the typical speed--density curves, revealing the existence of a pedestrians density optimizing the escape. We study both the discrete particle dynamics as well as the corresponding hydrodynamic limit (a porous medium equation and a transport (continuity) equation). We also point out the dependence of the effective transport coefficients on the two thresholds -- the essence of the microstructure information

    Animal moral psychologies

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    Observations of animals engaging in apparently moral behavior have led academics and the public alike to ask whether morality is shared between humans and other animals. Some philosophers explicitly argue that morality is unique to humans, because moral agency requires capacities that are only demonstrated in our species. Other philosophers argue that some animals can participate in morality because they possess these capacities in a rudimentary form. Scientists have also joined the discussion, and their views are just as varied as the philosophers’. Some research programs examine whether animals countenance specific human norms, such as fairness. Other research programs investigate the cognitive and affective capacities thought to be necessary for morality. There are two sets of concerns that can be raised by these debates. They sometimes suffer from there being no agreed upon theory of morality and no clear account of whether there is a demarcation between moral and social behavior; that is, they lack a proper philosophical foundation. They also sometimes suffer from there being disagreement about the psychological capacities evident in animals. Of these two sets of concerns—the nature of the moral and the scope of psychological capacities—we aim to take on only the second. In this chapter we defend the claim that animals have three sets of capacities that, on some views, are taken as necessary and foundational for moral judgment and action. These are capacities of care, capacities of autonomy, and normative capacities. Care, we argue, is widely found among social animals. Autonomy and normativity are more recent topics of empirical investigation, so while there is less evidence of these capacities at this point in our developing scientific knowledge, the current data is strongly suggestive

    Size Matters: Microservices Research and Applications

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    In this chapter we offer an overview of microservices providing the introductory information that a reader should know before continuing reading this book. We introduce the idea of microservices and we discuss some of the current research challenges and real-life software applications where the microservice paradigm play a key role. We have identified a set of areas where both researcher and developer can propose new ideas and technical solutions.Comment: arXiv admin note: text overlap with arXiv:1706.0735

    Collective behavior in slave-making ants: how ecology and social structure shape raiding strategies

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    In this dissertation, I studied the raiding behavior of a slave-making ant, Temnothorax americanus, a social parasite whose workforce consists of different ant species. ‘Slave’ workers are acquired in coordinated raids during which slave-maker workers attack a host colony and steal the immatures (brood). I focused on the mechanisms colonies use to reach collective decisions over where raid and on the attack once a raiding site was chosen. In Chapter One, I first established which nest characteristics make an optimal raiding choice by measuring the benefit of raids (stolen brood), and counterbalancing costs (mortality), at target colonies that differed in the number of brood, workers, or their ratios. These experiments showed that slave-makers are more successful when attacking colonies where brood outnumber workers and where there is an intermediate number of workers. In Chapter Two, I tested whether slave-maker colonies demonstrate a preference for such nests and characterize their decision-making strategy. Choice trials showed that slave-maker colonies exhibit no preference over host colony features. This result led to the question of why not be more selective? I then tested for ecological conditions that could favor their low acceptance threshold and show that slave-maker colonies encounter host colonies at a very low rate relative to the time when brood is available to raid. Slave-maker colonies therefore ought to raid every nest they find rather than pay the opportunity cost of waiting to raid only the best host colonies. In Chapter Three, I investigated the mechanisms of attack and show that successful raiding parties effectively evacuate workers while guarding the door to keep the brood inside. I also tested how conflict, especially prominent in T. americanus colonies, affects this collective behavior. I found that workers from colonies with higher levels of worker reproduction initiate attacks alone rather than as a group. In Chapter Four, I explored how cooperation and collective behaviors co-evolve by modeling these interactions analytically. I adapted mathematical models of cooperative binding from biochemistry to characterize collective behaviors that arise in a non-linear fashion

    Capturing Individual Harms

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    The aggregated lifestyles and behaviors of individuals impose significant environmental harms yet remain largely unregulated. A growing literature recognizes the environmental significance of individual behaviors, critiques the failure of environmental law and policy to capture harms traceable to individual behaviors, and suggests and evaluates strategies for capturing individual harms going forward. This Article contributes to the existing literature by approaching the problem of environmentally significant individual harms through the lens of environmental federalism. Using climate change and individual greenhouse gas (“GHG”) emissions as an exemplar, the Article illustrates how local information, local governments, and local implementation can enhance policies designed to capture individual environmental harms. Local information and community-level implementation may enhance norm management efforts designed to influence GHG-emitting behaviors by (1) allowing for the identification of concrete behaviors that are feasible to target through norm management in a given community; (2) informing the design and content of norm campaigns, including the selection of the abstract norm that will form the basis of the appeal for specific behavioral change; and (3) facilitating effective implementation strategies. This framework supports a preference for local action expressed, but to date largely unexamined, in the broader norm management literature. Additionally, the Article argues that obstacles to using mandates to influence GHG-emitting behaviors may be less formidable when mandates are developed and enforced locally. Local development and enforcement of mandates can reduce intrusion objections because (1) individuals are accustomed to local control over day-to-day behaviors; (2) familiarity with local attitudes and practices enables the design of mandates that avoid intrusion objections; and (3) local governments are in a better position to structure time, place, and manner restrictions that channel behavior while preserving some individual choice. Local design and enforcement of mandates may also minimize the key enforcement challenges of expense, numerosity, and (in)visibility

    Rendering sustainable consumer behavior more sustainable : psychological tools for marketing pro-social commitment.

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    This dissertation deals with persuasive communication in the context of social marketing, which is a field devoted to the promotion of socially desirable behavior. We focused on the promotion of pro-environmental behavior. The decision whether or not to behave environmentally friendly confronts the individual with a social dilemma. This is a choice between an option that serves the collective interest and an option that serves his or her self-interest. Choosing the environmentally friendly option is in the interest of others (e.g., the community, society, even future generations) but is often associated with a cost to the individual, like money, time, effort, or inconvenience. Therefore, convincing an individual to behave environmentally friendly implies persuading him or her to pursue the interest of others at the cost of his or her immediate self-interest. The social marketing approach traditionally relies on the assumption that successful behavioral change towards serving the collective interest, directly follows from having people think about the consequences of behavioral alternatives. Informational and educational campaigns based on this idea have indeed been very successful at generating awareness and concern about environmental issues, but, in contrast, disappointingly unsuccessful at making people change their behavior. We propose an complementary approach that consists of activating the right pro-environmental value in a more subtle way. We found, using laboratory games with a social dilemma structure, that decisions can be based on either an intuitive or a more rational system. People with pro-social values tend to behave more pro-socially than people with pro-self values when they followed their intuitive system. However, when thinking more rationally, pro-socials and pro-selfs behaved equally selfishly. Thinking seems to enable individuals to find justifications for behaving selfishly. Therefore we present two persuasion techniques, which do not motivate people to think, but which simply suggest or remind people that they hold pro-environmental values. Positive cueing reminds people of cases in which they behaved pro-environmentally in the past, and social labeling describes a person as being concerned with the environment. Both tools were more successful at producing more environmentally friendly behavior than educational campaigns.

    The virtual and the disconnected: an analysis of our 21st century perceptive behaviors and their effects on communication and visual culture

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    How do we percieve the world?’ Through research and literary review, as well as reflection on personal experience and culture, I have come to develop temporary notions that will be tested and analyzed through further methodology and experimentation. I am supporting the notion that we live in a highly post-modernist society, living liquid lives and experiencing entirely interconnected relationships with our social and technological milieus. Hence the way we percieve the world is highly different to societies preceding our exponential development. First of all our immediate perception of our surroundings is altered by the changing visual environment of our lives in design, technology, and social developments. Secondly, our psychological perception of the rest of the world is strongly influenced by the nature of our current 21st century endeavors. We continue to develop a deep knowledge and understanding of our coexistence with images and technology. More and more, these entities are proving themselves to be omnipresent in our culture and are gravitating away from our complete control of them. The development of the notion of ‘others’ in our mind has evolved from previous societies, aided as well by the intricately wired and connected social network we have created for ourselves. This, as well as all aforementioned developments, has engendered a visibly strengthened and diverse individualism that contrasts with our flourishing homogenization. Conversation with the others and with the self has become a virtual construct. All these happenigs have occured due to the accelerated development of a technologically and socially fragmented, postmodernist environment. My intent is to ultimately represent visually the altered perceptive behaviors and undertandings of our current society in a visual composition that comprises all notions developped during the thesis
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